1. Field of the Invention
The present invention relates to a radial flow machine, such as a centrifugal compressor and a centripetal turbine operating on a reverse principle thereto. In particular, the present invention relates to a high efficiency centrifugal compressor able to compress a relatively small amount of fluid, and to compress liquidified gas for a supply of hot water, heating and cooling air, and refrigeration.
2. Description of the Related Art
Compressors are classified as reciprocating compressors, rotary compressors, and centrifugal compressors. The volumetric efficiency of the reciprocating compressor and the rotary sleeve type compressor having an eccentric piston is low because of mechanical loss due to piston friction, a wear, power losses caused by an increase in the temperature of a sucked fluid, and residual compressed fluid remaining in the cylinder. Also, lubricating oil is circulated in the compressor together with the fluid to be compressed, and the pressure loss in the circulating lubricating oil is high and further the lubricating oil is mixed with the fluid to be compressed, which causes a deterioration of the properties of the fluid.
A screw type compressor suffers from mechanical loss when driving the rotors synchronously, a pressure loss when circulating a large amount of lubricating oil, a loss of the fluid to be compressed due to leakage, and a rotational friction between the screws and the fluid to be compressed or the lubricating oil. Also, the properties of the lubricating oil are deteriorated. Accordingly, the lubricating oil should be separated from the fluid to be compressed, but this increases the initial costs and running costs.
In a centrifugal compressor, however, the mechanical loss occurs only at the bearings, and thus it is not necessary to circulate the lubricating oil. Nevertheless, the centrifugal compressor has a construction problem in that a loss by leakage of the fluid from the outlets toward the inlets of the impeller, and the rotational friction loss at the disks are high, since a difference between the pressure in the outlets and the pressure in the inlets of the impeller is large, an amount of backflow from the diffuser to the impeller is large, and leakage occur through a clearance between the impeller and the impeller casing. This problem can be dealt with only by constructing a centrifugal compressor having a large capacity, to thereby reduce the loss relative to an enlarged capacity. Conversely, this relative loss will become large when the capacity of the centrifugal compressor is small and, for example, the centrifugal compressor can not function at a capacity of less than 25 refrigeration tons. This is because, if a conventionally arranged centrifugal compressor has a small capacity, the friction in the flow channels in the impeller becomes greater, and a high speed flow of the fluid can not be obtained at the outlets of the impeller due to this increased friction. This further causes an increase in static pressure at the outlets of the impeller, which in turn causes an increase in the backflow from the diffuser. It may also become necessary to reduce the number of vanes of the impeller if the centrifugal compressor has a small capacity, and in this case, there exist portions at the outlets of the impeller at which a static pressure is locally high. Namely, when static pressure at the outlets of the impeller becomes high, leakage loss around the impeller and rotational friction loss become large, and thus the centrifugal compressor no longer operates as required since it does not substantially compress the fluid but still consumes power. Accordingly, a centrifugal compressor with a small capacity has not been produced.
In addition, in a conventionally arranged centrifugal compressor, it is difficult to deal with shock waves and establish a high compression ratio at a single stage, and therefore, a multistage centrifugal compressor must be used when a high compression ratio is required. In this case, it is difficult to completely seal the shaft, and thus the compressed fluid flows back from the higher pressure stage to the lower pressure stage. The leakage loss and loss of power at the shaft seals are large but cannot be avoided.
In addition, the backflow of the fluid from the higher pressure stage to the lower pressure stage is accompanied by a backflow of heat, causing an increase in enthalpy to thereby necessitate a greater head, and thus a further loss of power.
If the above described problems could be solved and a centrifugal compressor having a small capacity produced, this would provide a very effective and ideal centrifugal compressor.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-described problems and provide a centrifugal compressor in which a friction of the fluid in the flow channels of the impeller during acceleration is lowered, and a high speed flow with an averaged low static pressure is established at the outlets of the impeller.
A further object of the present invention is to provide a centrifugal compressor in which a difference between the pressure in the outlets and the pressure in the inlets of the impeller is lowered, and the pressure around the impeller is reduced while maintaining a pressure equilibrium at the outer circumferential surface and the inner circumferential surface of the impeller, respectively, to thereby prevent leakage and reduce the rotational friction of the disks.
Another object of the present invention is to provide a centrifugal compressor comprising a diffuser in which a backflow of the fluid is prevented and the high speed fluid is converted to fluid having a high total pressure while maintaining the static pressure in the outlets of the impeller at a low level. The diffuser is made from a heat insulating material, to increase the effectiveness of the compression, and the fluid to be compressed is composed of mixed components.
A still further object of the present invention is to provide a centrifugal compressor in which the injected fluid is under-expanded at the outlets of the impeller and forms a fluid layer with a supersonic velocity, and the resulting shock wave is extinguished at the diffuser, and thus it is possible to develop a supersonic centrifugal compressor in which a high compression ratio can be obtained at a single stage, or a multipurpose centrifugal compressor in which the flow rate can be varied in accordance with a desired head. Accordingly, the objects of the present invention are to realize an efficient centrifugal compressor having a small capacity and to increase the efficiency of a centrifugal compressor having a large capacity.
Fundamentally, heat stems from any particle which is self-vibratory and it is the force that causes other particles to vibrate. Accordingly, any electromagnetic wave which exerts a vibrating force will generate heat. The flow of heat is a transmission of this vibration, so that the higher the number of vibrations the higher the temperature, and the greater the amplitude of vibration, the stronger the heat. Also, the vibrating particle sympathizes at a proper vibration. To increase the temperature by compressing fluid is to increases the number of vibrations from the compressed fluid, and a frictional heat is due to a vibration of molecules by excitation.
A heat insulating material absorbs the vibration of molecules, and heating and cooling are effects caused by a difference in the number and amplitude of a vibration of sensitive cells.
To attain the above objects, according to a first aspect of the present invention, the impeller comprises at least one nozzle at the outlet of each of the flow channels thereof, and a contraction at the inlet of each of the flow channels thereof, so that each of the flow channels between the at least one nozzle and the contraction is a low speed flow channel. By this arrangement, it is possible to reduce a friction of the fluid in the impeller and to obtain a high speed flow of the fluid at the outlets of the impeller, whereby a kinetic energy of the fluid is increased at the outlets of the impeller while a static pressure thereat is lowered, to thus lower a reaction grade. Also, by slowing down the relative velocity of the fluid in the low speed flow channel, it is possible to obtain an averaged speed at the inlets of the nozzles of the impeller.
The contraction at each inlet of the impeller serves to reduce a friction of the fluid at the inlet of the impeller, and to increase the relative velocity of the fluid at the inlet of the impeller, to contribute to an increase of the relative velocity of the fluid at the outlet of the impeller, allowing the construction of an impeller with a small diameter and enabling a reduction of the rotational disk friction. The inflow direction of the fluid at the inlet of the impeller is selected such that the flow of fluid prevents a rotation of the fluid in the low speed flow channel, to thereby average the speed of the fluid in the low speed flow channel at the inlets of the nozzles of the impeller.
The nozzle preferably comprises a supersonic nozzle (convergent-divergent nozzle) to obtain a supersonic flow of the fluid. The supersonic nozzle preferably comprises an under-expansion nozzle to suppress an occurrence of a shock wave, and thus enable a single stage compressor with a large compression ratio to be obtained.
Preferably, a variable adjusting device is provided for variably adjusting an angle of the inflowing direction or the outflowing direction of the fluid in the impeller, or for variably adjusting a cross section of the inlet or the outlet of the impeller in accordance with a required head of the fluid, to level the load and thereby save power, whereby a multipurpose centrifugal compressor can be obtained. For example, the inlet or the outlet of the impeller is provided with an elastic means deformable under a centrifugal force.
Preferably, fluid layer averaging vanes are concentrically and consecutively provided on the peripheries of the side discs of the impeller, to form a circumferentially averaged fluid layer with a uniform pressure and a uniform outflowing direction. The fluid layer averaging vanes preferably comprise expansion vanes with a constant expansion factor in which the fluid continuously expands from the inlet to the outlet of the fluid layer averaging vanes, and preferably such vanes are under-expansion vanes. Also, a variable adjusting device is provided for variably adjusting a cross section of the fluid flowing through the layer averaging vanes. This variable adjusting device preferably comprises an elastic valve deformable under a centrifugal force and thus able to adapt to changes in the amount of the fluid flow.
Preferably, the distance from the axis of the rotatable shaft to the inlet of the impeller is greater than that from the axis of the rotatable shaft to the inner circumferential surface of the side disc, to slow down the absolute speed of the fluid at the inner circumferential surface of the side disc at which the impeller is sealingly surrounded by the impeller casing. Preferably, a circumferential pressure increasing projection is provided concentrically and consecutively on this inner circumferential surface of the side disc, the circumferential pressure increasing projection projecting from the inner circumferential surface into the flow of the fluid, to bring a total pressure to the inner circumferential surface and increase a static pressure thereat, to thereby lower a pressure difference between the inner circumferential surface and the outer circumferential surface of the impeller. The circumferential pressure increasing projection preferably has a spoon-shaped cross-section with a shapened end tip projecting inward of the flow channel, to mitigate a shock of the fluid.
Preferably, a means for adjusting the position of the impeller is provided to obtain a smooth fluid flow toward the diffuser. Also, the impeller casing is preferably surrounded by thermally insulating materials.
Preferably, the fluid to be compressed comprises at least one component selected from the group listed in the appended claims, and the selected component includes all substitutes and isomers thereof. The fluid to be compressed is preferably selected from mixed fluid components, to disperse the energy of a shock wave of the fluid to be compressed and decrease its entropy, to thereby save the power and increase the heat transportation.
According to the second aspect of the present invention, backflow preventing and friction reducing projections are provided concentrically in the inner surface of the impeller casing around the axis of the rotatable shaft. By this arrangement it is possible to prevent a backflow leakage through a space between the impeller and the impeller casing from the outer circumferential surface to the inner circumferential surface of the impeller and reduce the leakage pressure, and thus reduce the rotational disk friction.
More particularly, by providing the backflow preventing and friction reducing projections, the fluid rotates around the impeller therewith and forms a boundary layer around the impeller, which is locally inclined to prevent the backflow, and thus rotational disk friction is reduced.
The end tips of the backflow preventing and friction reducing projections protrude into a portion of the high speed rotating fluid of the thick boundary layer around the impeller, so that the boundary layer is split into a plurality of streams which separately flow between the adjacent backflow preventing and friction reducing projections, in which a portion near to the end tip (near to the impeller) of the backflow preventing and friction reducing projection has a high speed head due to a centrifugal force, directed radially outwardly of the impeller, and another portion near to the root (near to the impeller casing) thereof has a slow speed head; the fluid of this slow speed portion being entrained and accelerated by the fluid of the high speed portion, to thereby average the head therebetween. Therefore, the pressure around the impeller is reduced, and simultaneously, the backflow leakage through a space between the impeller and the impeller casing from the outer circumferential surface to the inner circumferential surface of the impeller is prevented. In this way, backflow is prevented and only the flow of fluid radially outwardly of the impeller remains effective, so that the density of the fluid spirally rotating between the projections becomes smaller as it becomes nearer to the rotating shaft, and thus rotational disk friction is reduced.
Preferably, each of the backflow preventing and friction reducing projections has a spoon-shaped cross section and a wall between the backflow preventing and friction reducing projections has a rounded shape, by which a friction of the spirally rotating fluid is reduced.
Preferably, a clearance adjusting device is provided for making a clearance between the backflow preventing and friction reducing projections and the side disc of the impeller as small as possible, and thus increase the backflow preventing effect and rotational disk friction reducing effect. In this case, the backflow preventing and friction reducing projections are preferably electrically insulated from the impeller casing, to enable a clearance adjusting operation without contact between the projections and the impeller, while applying a voltage between the projections and the impeller.
Preferably, a pressure detecting device is provided in the inner wall of the impeller casing to adequately reduce the pressure around the impeller, and the operation of the compressor can be stopped when an excessive pressure due to surging is detected.
According to the third aspect of the present invention, leakage preventing and pressure reducing projections are provided between the side disc and the impeller casing; the leakage preventing and pressure reducing projections being rotatable with the rotatable shaft. By this arrangement, an excess or insufficient rise of a static pressure due to the rotational disc friction can be compensated to prevent leakage around the impeller and to reduce the rotational disc friction by lowering the pressure around the impeller.
Preferably, each of the leakage preventing and pressure reducing projections has a sharpened edge in a cross section of the fluid flow, to mitigate a shock of the flowing fluid, and preferably has a spoon-shaped cross section to allow the head of the fluid to be further enlarged.
Preferably, the leakage preventing and pressure reducing projection are cantilevered vanes, to shorten the passage of the backflow fluid and to accelerate the backflow fluid before it is decelerated by friction, and thus reduce the power needed for acceleration.
Preferably, backflow returning projections are provided at the fluid inlets of the leakage preventing and pressure reducing vanes, the backflow returning projections being fixed to the impeller casing concentrically and consecutively about the rotatable shaft, to return the back flow fluid to the fluid inlets of the leakage preventing and pressure reducing vanes.
The leakage preventing and pressure reducing vanes are arranged between the side disc of the impeller and the impeller casing such that the total pressure at the circumferential inner and outer surfaces of the impeller, including a rise in the static pressure due to a rotational disc friction, generally equals the inlet and outlet pressures in the impeller, respectively. The leakage preventing and pressure reducing vanes are arranged at the circumferential inner and outer surfaces of the impeller, i.e., at an inner central opening and an outer opening between the side disc of the impeller and the impeller casing. By this arrangement, the pressure around the impeller is further reduced. The leakage preventing and pressure reducing vanes prevent leakage from the outer opening to the inner central opening and from the inner opening to the outer central opening.
The leakage preventing and pressure reducing vanes maintain a pressure equilibrium within a designed range such that the total pressure of a static pressure caused by a rotational friction of the disc of the impeller and a static pressure caused by rotation of the leakage preventing and pressure reducing vanes at the circumferential inner and outer surfaces of the impeller generally equals the inlet and outlet pressures in the impeller, respectively. More particularly, if the inlet and outlet pressures in the impeller are higher than the above described pressures, respectively, the fluid flows back from the inlet and outlet of the impeller, respectively, to the space around the impeller, then the back-flowing fluid is returned to the respective inlets of the leakage preventing and pressure reducing vanes by the backflow returning projections. Accordingly, if the amount of backflow fluid is increased the head of the backflow fluid is increased, since the backflow fluid is accelerated by the leakage preventing and pressure reducing vanes, and thus the increase of the head of the fluid around the impeller causes a reduction of the backflow fluid from the inlet and outlet of the impeller, to thereby reach a pressure equilibrium. This pressure equilibrium is established when the fluid circulates from and to the outlet and the inlet of the leakage preventing and pressure reducing vanes with a circulating pressure which is far lower than the head of the fluid compressed in the impeller. The cantilevered vanes can shorten this circulation passage. Alternatively, if the inlet and outlet pressures in the impeller are lower than the pressures around the impeller, respectively, the pressures around the impeller are reduced and a pressure equilibrium is attained. In this case, an equilibrium is attained in which the fluid retained between the leakage preventing and pressure reducing vanes rotates with the leakage preventing and pressure reducing vanes. A maximum efficiency is obtained when such an equilibrium is attained at both the inner opening and the outer opening of the impeller, and the compressor is designed such that this is a normal operating condition.
In this way, the function of the leakage preventing and pressure reducing vanes adapt themselves to the varying pressure of the inlet and the outlet of the impeller, from the maximum circulating equilibrium at the inner opening to the maximum circulating equilibrium at the outer opening. But if the pressure difference exceeds a designed value, the space around the impeller functions as a bypass to automatically serve as a surging device.
Each of the backflow returning projections has a spoon-shaped cross section with a sharpened edge, and a wall between the backflow returning projections has a rounded shape, to reduce friction of the fluid and smooth the flow of the fluid.
The backflow returning projections are electrically insulated from the impeller casing and a clearance adjusting means is provided for the backflow returning projections to enable a clearance adjusting operation without contact between the backflow returning projections and the leakage preventing and pressure reducing vanes while applying a voltage therebetween. It is thus possible to make a clearance between the backflow returning projections and the leakage preventing and pressure reducing vanes as small as possible, and thus increase a backflow returning effect.
Preferably, a pressure averaging chamber is provided at the outlet of the leakage preventing and pressure reducing vanes, to level the pressure of the flowing-out fluid.
According to the fourth aspect of the present invention, the diffuser has an annular contraction and an annular divergent channel on the downstream side of the annular contraction, concentrically provided in the circumferential flow channel of the diffuser. A circumferential fluid collecting means is connected at an outer end of the circumferential flow channel of the diffuser, a cross-sectional area of the flow channel at the outlet of the annular divergent channel being greater than that of the flow channel at the largest cross-sectional region on the upstream side of the annular contraction. By this arrangement, the boundary layer of the fluid becomes thin at this annular contraction and thus the backflow therethrough is prevented, while converting the fluid from the impeller to the fluid having a high total pressure and maintaining a low static pressure at the outlet of the impeller.
The annular divergent channel is a flow channel in which the cross-sectional area thereof is gradually opened toward the downstream side thereof.
In the case of a subsonic diffuser, the annular contraction is located at the inlet of the flow channel of the diffuser. In the case of the supersonic diffuser, the annular contraction is located midway in the flow channel of the diffuser.
Preferably, annular backflow returning projections are provided in the side walls forming the flow channel of the diffuser at the inlet thereof, to return the fluid flowing back in the boundary layer. This back flowing fluid is then entrained by the high speed fluid again into the diffuser, to thereby prevent the back flow. In the subsonic diffuser, the annular backflow returning projections are located in the annular contraction.
Preferably, an annular rotation averaging flow channel is provided on the downstream side of the annular divergent channel. By this arrangement, the fluid flowing from the annular divergent channel moves rotatingly in this annular rotation averaging flow channel, averaging the pressure by the rotating fluid itself, with the resulting centrifugal force acting against the variety of the pressure in the circumferential fluid collecting means to thereby reduce the pressure at the outlet of the annular divergent channel and to ensure a constant outflow speed of the fluid and a constant outflow angle at the outlet of the annular divergent channel.
In the case of the supersonic diffuser, a cross-sectional area of the flow channel at the outlet of the annular divergent channel is greater than that of the flow channel at the largest cross-sectional region on the upstream side of the annular contraction, to displace a shock wave to a position on the downstream side of the annular contraction, and thereafter allow the shock wave to approach the annular contraction. By this arrangement, it is possible to convert the fluid from the impeller to the fluid having a high total pressure, while maintaining the speed of the fluid at the inlet of the diffuser at a supersonic level, and thus the static pressure at the outlet of the impeller at a low level. Further, preferably a cross-section of the annular contraction is variable, and in this case, it is possible to convert the fluid from the impeller to the fluid having a higher total pressure, and thus obtain a maximum diffuser efficiency, by further narrowing the annular contraction. In this case, the annular contraction is adjusted to allow the shock wave to approach the annular contraction, to thereby substantially extinguish the shock.
In the flow of the fluid in the supersonic diffuser, since the layer of the supersonic fluid from the impeller flows in the diffuser in an under-expansion fluid state, an expansion wave occurs at the inlet of the diffuser. This expansion wave is reflected at a boundary face of the boundary layer and a compression wave occurs. This compression wave grows to an oblique shock wave, and further, to a normal shock wave, and interferes with the boundary layer to generate a pseudo shock wave. This pseudo shock wave is simply called a shock wave. When this shock wave occurs on the upstream side of the annular contraction, by gradually reducing the pressure of the fluid at the outlet of this compressor, the shock wave is displaced from the largest cross-sectional region on the upstream side of the annular contraction (at which the layer of the supersonic fluid in the under-expansion state fully expands) to a region on the downstream side of the annular contraction where a cross-sectional area of the flow channel equal the largest cross-sectional region on the upstream side of the annular contraction. Here, by gradually increasing the pressure of the fluid at the outlet of this compressor, the shock wave is weakened and continuously approaches the annular contraction. In this condition, the fluid on the upstream side of this weak shock wave flows at a supersonic velocity, and the fluid on the downstream side of this weak shock wave flows at a subsonic velocity. Accordingly, the fluid flow is decelerated from the supersonic velocity to the subsonic velocity, and thus the high speed fluid is converted to the fluid having a high total pressure.
In addition, the cross-sectional area of the annular contraction is narrowed by operating the cross-sectional area varying means, and the pressure of the fluid at the outlet of this compressor is again gradually increased, so that the fluid flow is choked at the annular contraction to a sonic velocity and the weak shock wave is finally extinguished, and thus the high speed fluid is converted to the fluid having highest total pressure, and this compressor begins to operate normally. In the normal operation of the compressor, however, the fluid flow may be actually choked to a sonic velocity at a position slightly downstream of the annular contraction, since the fluid has a viscosity, and thus the cross-sectional area varying means of the annular contraction is adjusted so that the fluid flow is choked to a sonic velocity at a position closest to the annular contraction, whereby the boundary layer is the annular contraction is thinnest and thus a maximum backflow preventing effect and the maximum diffuser effect are obtained.
When the cross-sectional area of the annular contraction is not varied, it is possible to obtain an effect similar to that obtained by operating the cross-sectional area varying means, by varying the flow quantity or the Mach number. For example, by using the impeller of the above described first aspect of the present invention, it is possible to increase the Mach number, decrease the flow quantity and heighten the total pressure on the upstream side of the contraction whereby, without a change of the cross-sectional area of the annular contraction, it is possible to displace the shock wave from a region on the upstream side of the annular contraction to a region on the downstream side of the annular contraction. Thereafter, the Mach number, the flow quantity, and the upstream total pressure are gradually returned to the desired normal values to allow the shock wave to approach the annular contraction.
Preferably, the diffuser includes flow channel inlet forming members, and variable adjusting devices are provided for changing the positions of the flow channel inlet forming members, to coincide the inlet of the diffuser with the flowing-in fluid layer in correspondence with the thickness of the fluid layer.
Preferably, variable adjusting devices are provided for changing a cross-sectional area of the circumferential flow channel of the diffuser on the downstream side of the annular divergent channel, to thereby adjust the cross-sectional area of the annular divergent channel to a proper value to prevent the backflow, and to maintain the static pressure in the outlet of the annular divergent channel at a lower level.
In addition to an adjustment of the cross-sectional area of the inlet of the diffuser, the cross-sectional area of the annular contraction, and the cross-sectional area of the circumferential flow channel of the diffuser on the downstream side of the annular divergent channel, it is possible to adjust the cross-sectional area of the other portions of the diffuser in correspondence with a change of the flow quantity.
The diffuser may comprise an elastic valve constituting a deformable wall portion of the flow channel of the diffuser, to change the cross-sectional area of the flow channel of the diffuser by the action of the elastic valve and the pressure of the fluid in the compressor.
A shock wave detecting means may be provided in the flow channel of the diffuser and it is possible to change the pressure of the outlet of the compressor, the cross-sectional area of the annular contraction, and the flow quantity and the Mach number of the supersonic fluid in response to the position of the shock wave, to bring the shock wave near to the annular contraction and thus substantially extinguish the shock wave. The shock wave detecting means may be constituted by, for example, a device detecting an illuminance of a light passed through a shock wave and a difference between the pressures on the upstream and the downstream sides of a shock wave.
A pressure detecting means may be provided in the flow channel of the diffuser to appropriately control the operation of the compressor, or to find the shock wave in response to the detected pressure.
A pressure detecting means may be provided for detecting a pressure of flowing-in fluid to the impeller to determine the head of the impeller in response to the detected pressure, or to control the operation of the compressor with the maximum efficiency in response to a difference between the pressures in the impeller and in the diffuser.
Also, a pressure detecting means is provided for detecting a pressure of flowing-out fluid from the circumferential fluid collecting means to determine the revolution of the impeller, or to control the operation of the compressor with the maximum efficiency in response to a difference between the pressures in the diffuser and in the circumferential fluid collecting means or in response to the position of the shock wave.
A revolution detecting means may be provided for detecting a revolution of the impeller to control the Mach number or the variable adjusting members in response to signals from the revolution detecting means. The revolution detecting means may be constituted by, for example, a device receiving an electric signal from a magnetic sensor.
Also, a position detecting means may be provided for detecting a position of a variable portion of the circumferential flow channel of the diffuser, to detect a reference position and a displacement therefrom of the variable portion.
Preferably, the diffuser includes flow channel inlet forming members which are electrically insulated from the impeller. Also, the diffuser includes flow channel forming opposed side walls, which are electrically insulated from each other. By these arrangements, it is possible to assemble these members while adjusting the relative positions between the opposing members, by determining a contract between the opposing members while applying a voltage therebetween to thereby select respective reference positions. It is also possible to determine the positions of the above described members during the operation of the compressor, from a change of an electric capacity.
Preferably, the operation of the compressor is electronically controlled. This electronical control is carried out by a computer having a known hardware system, and software, and included in another electronical control system using the compressor of the present invention. This electronical control is carried out by the steps of, for example, detecting the revolution of the impeller with the use of an electromagnetic induction, driving a drive motor in response to a signal therefrom, controlling the Mach number, and changing the positions of the variable portions with the use of a digital micrometer having a revolution detecting means. The variable portions are returned to the respective reference positions when the compressor, is stopped, and the variable portions are moved to respective particular positions in accordance with the revolution of the impeller.
Preferably, sharply streamlined guide vanes are arranged in the circumferential flow channel of the diffuser, to guide the fluid therealong and to assist the fluid to flow smoothly when the flow rate is small.
In this case, in which the guide vanes are arranged in a portion of the circumferential flow channel of the diffuser where the fluid flows at a supersonic velocity, preferably the guide vanes have inlet ends having swept back angles, to reduce a friction of the fluid and to weaken the shock wave. Since the supersonic fluid layer flows radially from the impeller into the diffuser, the angle of deflection at the guide vanes becomes small and the inclination of the shock wave also becomes small, so that the shock wave is weakened. Also, since the fluid flows out from the impeller in an under-expansion state and flows in the diffuser, accompanying the expansion wave, the shock wave interferes with this expansion wave and is further weakened.
A cross-sectional area of the circumferential fluid collecting means may become gradually larger toward an output thereof, to level the pressure in the circumferential fluid collecting means to thereby affect an influence of the averaged pressure on the fluid of the upstream side. Also, the circumferential fluid collecting means has a plurality of outputs, to level the pressure in the circumferential fluid collecting means.
A check valve may be provided in the circumferential fluid collecting means at an output thereof to prevent a surging caused when the flow rate of the compressor is decreased, and to prevent a backflow of high pressure fluid and a backflow of heat when the compressor is stopped.
A position adjusting device may be provided for adjusting the position of the casing relative to a further main casing, to adequately determine the position of the annular contraction and the position of the inlet of the diffuser during assembly of the compressor.
The diffuser may be made from thermally insulating material, to prevent a backflow of heat and loss of heat and thereby prevent wasteful compression work and save power.
The fluid to be compressed can be selected from the group, listed in the appended claims, as described previously, and the selected component includes all substitutions and isomers thereof; for example, methylamine includes dimethylamine (ethylamine).
The fluid to be compressed can be used without mixing, but preferably a fluid component adapted to be compressed is mixed with a fluid component adapted to save power. The mixed fluid comprises at least two fluid components more active to each other. Fluid component flows under respective partial pressures, and thus it is possible to increase the heat transporting capacity.
The compression in the compressor surrounded by the thermal insulator can be deemed to be an adiabatic compression, and in particular an irreversible adiabatic compression, since friction and a vortex arise. Therefore, the whole entropy of the fluid to be compressed is increased in the course of compression. The mixed fluid according to the present invention serves to protect the fluid component, adapted to be compressed, from pyrolysis, to disperse the shock energy of this fluid component, and to decrease the entropy thereof, to thereby save power.